Process of the preparation of high-purity alkyladamantyl esters

ABSTRACT

There is provided a method for obtaining an alkyladamantyl ester efficiently by distilling and purifying a crude alkyladamantyl ester containing impurities which decompose the alkyladamantyl ester without decomposing the alkyladamantyl ester. 
     The crude alkyladamantyl ester such as crude 2-methyl-2-adamantyl methacrylate is distilled in the presence of a heterocyclic compound and/or a basic compound such as 3-ethyl-3-hydroxymethyloxetane or diglycidyl bisphenol A.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/JP01/04036 which has an Internationalfiling date of May 15, 2001, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention relates to a method for producing a high purityalkyladamantyl ester by distilling and purifying a crude alkyladamantylester containing impurities.

BACKGROUND ART

Heretofore, when a solution to be distilled which contains a targetcompound also contains materials which promote decomposition of thetarget compound despite the fact that the target compound is a compoundwhich is easily decomposed under influence of heat, a catalyst or thelike, the target compound is easily decomposed during distillation.Therefore, it is difficult to obtain the target compound at a highpurity or a high yield by purification by distillation. In general, evenif a very small amount of materials which exhibit a decompositionpromoting action is contained, it is very difficult to identify andremove the materials to such an amount that does not adversely affectthe target compound because they cause decomposition of the targetcompound at the time of heating. In such a case, a purification methodother than distillation must be used so as to purify a easilydecomposable target compound with good reproducibility and at a highpurity.

Meanwhile, demand for products of higher purity has been increasingevery year. In particular, a reduction in metal components of a productused in a semiconductor production process is strongly demanded. As apurification method which can remove such metal components efficiently,purification by distillation is suitable.

In recent years, it has been reported that polymers obtained fromalkyladamantyl esters having polymerizable groups have high dry etchingresistance in a semiconductor production process (refer to JP-A5-265212), and a possibility of their use as resist materials forsemiconductors has been receiving attention. When these alkyladamantylesters are used as resist materials for semiconductors, high purityalkyladamantyl esters having reduced metal components are required.

It is known that the alkyladamantyl ester can be produced by reacting2-alkyl-2-adamantanol or 2-alkylideneadamantane which is obtained via2-adamantanone from adamantane as a starting material or 2-adamantanonewith an organometallic reagent such as methyl magnesium bromide so as toobtain a metal alkoxide and reacting a carboxylic acid derivative suchas a carboxylic acid ester, a carboxylic anhydride or a carboxylic acidhalide or a carboxylic acid with the obtained metal alkoxide.

In general, the alkyladamantyl ester is easily decomposed whenstimulated by acid, heat or the like. For example, it is known that thealkyladamantyl ester is decomposed into a carboxylic acid or the likewhen heated in the presence of a catalytic amount of acid. By use ofsuch a characteristic, the alkyladamantyl ester is used as a rawmaterial for a chemically amplified resist in a semiconductor productionprocess. Therefore, to purify the alkyladamantyl ester by distillation,it is commonly practiced to wash the alkyladamantyl ester with an alkalisolution such as a sodium hydroxide solution as a pretreatment so as toremove acid components.

However, when a crude alkyladamantyl ester which has been subjected to aconventional pretreatment such as washing with an alkali solution so asto remove acid components is distilled by a commonly used method, thealkyladamantyl ester is decomposed during distillation for some reason,thereby producing a decomposition product such as a carboxylic acid or2-alkylideneadamantane. Thus, a high purity alkyladamantyl ester has notbeen able to be obtained at a good yield.

Further, it has been found that a crude alkyladamantyl ester or adistilled and purified alkyladamantyl ester is decomposed during storagefor some reason, thereby causing such a problem as coloration. Inaddition, it has also been found that an alkyladamantyl ester having apolymerizable group has a problem that when the alkyladamantyl ester isdecomposed during storage to have coloration, a molecular weight doesnot increase even if it is polymerized.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method for producinga high purity alkyladamantyl ester by applying an efficient purificationmethod to a crude alkyladamantyl ester for which an efficientdistillation and purification method has not been known.

The present inventor has made intensive studies so as to solve the aboveproblems. As a result, he has found that a crude alkyladamantyl estercan be purified efficiently by distilling the alkyladamantyl ester inthe presence of a heterocyclic compound and/or a basic compound and thatthe above compounds also have an effect of improving storage stabilityof the alkyladamantyl ester. The present inventor has completed thepresent invention by these findings.

That is, the present invention is a method for producing a high purityalkyladamantyl ester which comprises the steps of esterifying anadamantane compound having an —OH group, —OM group or ═R group (whereinM is an alkali metal atom or MgX (wherein X represents a halogen atom),and R is a divalent aliphatic hydrocarbon group) and distilling a crudealkyladamantyl ester obtained to form a high purity alkyladamantylester, wherein the distillation is carried out in the presence of aheterocyclic compound and/or a basic compound.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, a crude alkyladamantyl ester to be distilledis obtained by esterification of an adamantane compound having an —OHgroup, —OM group or ═R group (wherein M is an alkali metal atom or MgX(wherein X represents a halogen atom), and R is a divalent aliphatichydrocarbon group). The crude alkyladamantyl ester obtained by such aprocess contains an impurity which can decompose the alkyladamantylester. Although the impurity has not heretofore been identified yet, thepresent inventors assume that it may be a compound which decomposesunder distillation conditions and produces acid.

In the —OH group, —OM group or ═R group (wherein M is an alkali metalatom or MgX (wherein X represents a halogen atom), and R is a divalentaliphatic hydrocarbon group) in the adamantane compound which is a rawmaterial of the crude alkyladamantyl ester, the alkali metal atomrepresented by M is a potassium atom, a sodium atom or the like, and thehalogen atom represented by X is a chlorine atom, a bromine atom, aniodine atom or the like. Further, the divalent aliphatic hydrocarbongroup represented by R is exemplified by a divalent group having 1 to 4carbon atoms such as a methylidene group, an ethylidene group, apropylidene group, an isopropylidene group and the like.

Illustrative examples of the adamantane compound having the —OH group,—OM group or ═R group include 2-alkyl-2-adamantanol (wherein the alkylgroup has 1 to 6 carbon atoms) having an —OH group,2-alkylideneadamantane (wherein the alkylidene group has 1 to 4 carbonatoms) having an ═R group, and a compound represented by the followingformula (1)

(wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and M is an alkali metal atom or MgX (wherein X represents ahalogen atom)).

Illustrative examples of a specific production method of the crudealkyladamantyl ester include a method comprising the steps of alkylating2-adamantanone with a Grignard reagent such as an alkyl magnesium halideor an organometallic reagent such as alkyl lithium so as to obtain anadamantane compound having an —OM group and then esterifying theadamantane compound with a carboxylic acid halide; a method comprisingthe steps of alkylating 2-adamantanone with an organometallic reagent soas to obtain 2-alkyl-2-admantanol and then esterifying the compound witha carboxylic acid halide, carboxylic anhydride or carboxylic acid ester;and a method comprising the steps of alkylating 2-adamantanone with anorganometallic reagent, dehydrating an alcohol obtained fromdecomposition of a metal alkoxide so as to obtain 2-alkylideneadamantaneand then esterifying the compound with a carboxylic acid by means of anaddition reaction.

The crude alkyladamantyl ester may contain impurities other than theaforementioned impurity which decomposes the alkyladamantyl ester aslong as the impurities are those which can be separated by distillation.Illustrative examples of such impurities include adamantane and2-adamantanone which are used as a raw material upon synthesis of thealkyladamantyl ester, 1-adamantanol which is an impurity derived fromthe raw material, 1-adamatyl ester and 2-alkylideneadamantane which areby-produced at the time of the synthesis, and tetrahydrofuran and hexanewhich are used as a solvent at the time of the synthesis.

The content of these other impurities is not particularly limited. Whenthe crude alkyladamantyl ester is produced by any of the above methods,a total amount of the other impurities is about 1 to 50 parts by weightwhen the weight of the alkyladamantyl ester is 100 parts by weight.

As the alkyladamantyl ester to be purified in the present invention, acompound represented by the following formula (2):

(wherein R² is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and R³ is a hydrogen atom or a methyl group) is preferably used.

Illustrative examples of the alkyl group having 1 to 6 carbon atomswhich is represented by R² in the above formula (2) include linear alkylgroups such as a methyl group, ethyl group, propyl group, butyl groupand hexyl group; and branched alkyl groups such as an isopropyl group,tertiary butyl group and neopentyl group. In particular, analkyladamantyl ester represented by the above formula (2) in which R² isa methyl group, ethyl group or butyl group and R³ is a hydrogen atom ormethyl group is suitable since it is useful as a raw material for aresist for a semiconductor and a high degree of purification inparticular is important.

In the present invention, the above crude alkyladamantyl ester isdistilled in the presence of a heterocyclic compound and/or a basiccompound (hereinafter also referred to as “decomposition inhibitingmaterials”).

In the present invention, as the heterocyclic compound which is one ofthe decomposition inhibiting materials, a compound having, in amolecule, at least one heterocyclic ring having at least one hetero atomselected from the group consisting of oxygen, nitrogen, sulfur, seleniumand silicon and 2 to 6 carbon atoms as ring-member atoms is preferablyused. The heterocyclic compound may have a plurality of hetero atoms inthe same heterocyclic ring. Further, the heterocyclic compound may havea plurality of the same or different heterocyclic rings in a moleculeindependently, and may have heterocyclic rings as condensed rings of theheterocyclic rings or as condensed rings of the heterocyclic rings andaromatic hydrocarbon rings.

As the heterocyclic compound, a known heterocyclic compound may be usedwithout limitation. For example, such a compound as one described in“Chemistry of Heterocyclic Compound, Third Revised Edition” (publishedin 1980 by Kagaku Gijutsu Syuppansya) can be used.

As the heterocyclic ring contained in the heterocyclic compound in thepresent invention, a saturated three-to-five-membered ring is preferred.Illustrative examples of such a heterocyclic ring include cyclic etherssuch as oxirane, oxetane and oxolane; cyclic thioethers such asthiirane, thiethane and thiolane; cyclic amines or N-alkyl substitutionproducts thereof such as aziridine, N-methylaziridine and azetidine;cyclic siloxanes; and oxazines.

Of these, as a decomposition inhibiting material which exhibits a greateffect of inhibiting decomposition of the alkyladamantyl ester and withwhich a higher purity target compound can be obtained, a heterocycliccompound having a cyclic ether structure in a molecule can be used.Above all, when a heterocyclic compound containing an oxirane ring oroxetane ring is used, it generally provides an effective decompositioninhibiting effect even in a small amount.

As the heterocyclic compound containing the cyclic ether structure,known compounds can be used without particular limitations. As theheterocyclic compound having the oxirane ring, compounds such as thosedescribed in a section in the 14^(th) category (thermosetting resin) of“Chemical Commodity Product of 13599” (published in 1999 by KagakuKougyo Nippou Sya), in a section of the second chapter (epoxy resin) of“Epoxy Resin Handbook” (published in 1987 by Nikkan Kougyo Shinbun Sya)and in a section of the third chapter (special epoxy resin) of “NewEpoxy Resin” (published in 1975 by Syokodo) can be used.

Illustrative examples of such compounds include oxirane compoundssubstituted by an alkyl group or an aryl group such as propylene oxide,6,7-epoxydodecane, styrene oxide and α,α′-epoxydibenzyl; glycidyl ethercompounds (including monomers and oligomers formed from two or moremolecules) having a plurality of glycidyl groups such as phenyl glycidylether, glycerol diglycidyl ether, diglycidyl bisphenol A, brominateddiglycidyl bisphenol A, diglycidyl bisphenol C, tetraglycidylbenzophenone, diglycidyl bisphenol F, triglycidyl-p-aminophenol,diglycidyl cyclohexane 1,3-dicarboxylate and novolac-type epoxy;glycidyl ester compounds such as diglycidyl phthalate, diglycidyltetrahydrophthalate, diglycidyl hexahydrophthalate, glycidyl dimer acidester, diglycidyl hexahydrophthalate and diglycidyl-p-oxybenzoic acid;alicyclic epoxy compounds such as vinylcyclohexene dioxide and7-oxabicyclo[4.1.0]hepta-3-ylmethyl-7-oxabicyclo[4.1.0]heptane-3-carboxylate;glycidyl amine compounds such as tetraglycidyl diaminodiphenylmethane,triglycidyl p-aminophenol and diglycidyl aniline; and heterocyclicepoxys having other heterocyclic structures together with an oxiranering such as 1,3-diglycidyl hydantoin, glycidyl glycideoxyethylhydantoin and triglycidyl isocyanurate.

Further, illustrative examples of the heterocyclic compound having theoxetane ring include 3-ethyl-3-hydroxymethyloxetane and1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene.

The basic compound which is the other decomposition inhibiting materialis a compound which has an aqueous phase having a pH of larger than 7when mixed with water (when not easily dissolved in water, awater-insoluble organic solvent such as hexane is further added theretoand shaken). Illustrative examples of such a basic compound include anoxide or hydroxide of an alkali metal or alkaline earth metal such assodium hydroxide, potassium hydroxide, barium hydroxide, sodium oxide,magnesium oxide and calcium oxide; an inorganic weak base comprising aweak acid and a strong base such as potassium hydrogencarbonate,magnesium carbonate and sodium acetate; aluminum hydroxide and alumina;organic hydroxides such as tetramethylammonium hydroxide andtetrabutylammonium hydroxide; aliphatic amines such as triethylamine,trioctylamine, ethanolamine, diethanolamine and triethanolamine;aromatic amines such as pyridine, dimethylaminopyridine, phenothiazine,dibutylphenothiazine, dioctylphenothiazine,N,N′-diphenyl-p-phenylenediamine and N,N′-dinaphthyl-p-phenylenediamine;inorganic complex compounds such as hydrotalcite, e.g.,Mg₆Al₂(OH)₁₆CO₃.4H₂O and zeolite, e.g., A-type zeolite; Lewis bases; andthe like.

The above decomposition inhibiting materials are preferably those whichdo not react with the alkyladamantyl ester which is the target compoundand do not decompose under distillation conditions. Further, to obtain ahigh purity alkyladamantyl ester, these decomposition inhibitingmaterials are preferably those which are not distilled out together withthe target compound or can be easily separated from the target compoundto be distilled out even if contained in the target compound.

In order not to be distilled out together with the target compound, thedecomposition inhibiting materials preferably shows such a high boilingpoint that does not allow the decomposition inhibiting materials to bedistilled out at the time of distillation, has neither a boiling pointnor a sublimation point or shows such a low boiling point that does notallow the decomposition inhibiting materials to be distilled outtogether with the target compound. Particularly, to maintain thedecomposition inhibiting effect until completion of the distillation ofthe target compound, the decomposition inhibiting materials are morepreferably compounds which show such a high boiling point which does notallow the compounds to be distilled out at the time of the distillationor have neither a boiling point nor a sublimation point.

In a case where decomposition inhibiting materials which can be easilyseparated from the target compound are used, even when the targetcompound is distilled out and mixed with the decomposition inhibitingmaterials as the distillation proceeds, the target compound can beobtained at a high purity since the decomposition inhibiting materialscan be removed easily. For example, if the target compound does not havecompatibility with the decomposition inhibiting materials, the targetcompound can be obtained easily through liquid separation. Further, ifwater-soluble decomposition inhibiting materials are used when thetarget compound is insoluble in water, the target compound can beobtained easily by washing a distillate with water. Further, ifwater-insoluble decomposition inhibiting materials are used when thetarget compound is easily soluble in water, an acid solution or analkali solution, the target compound can be obtained easily bydissolving a distillate in water, an acid solution or an alkalisolution, removing the decomposition inhibiting materials by a liquidseparating operation or the like, performing a neutralization operationas required, and removing water. In addition, when the target compoundis insoluble in water and stable in acid or alkali, acid or alkalidecomposition inhibiting materials can be used. In this case, the targetcompound can be obtained easily by washing a distillate with an alkalior acid solution.

The decomposition inhibiting materials are added in an amount sufficientto maintain the decomposition inhibiting effect and inhibitdecomposition of the target compound. The amount of the decompositioninhibiting materials should be determined in consideration of an amountof decomposition promoting materials and is generally 0.0001 to 500parts by weight, preferably 0.1 to 10 parts by weight, based on 100parts by weight of the crude alkyladamantyl ester.

In the production method of the present invention, distillation of thecrude alkyladamantyl ester is carried out in the presence of thedecomposition inhibiting materials. A means for adding the decompositioninhibiting materials to the crude alkyladamantyl ester is notparticularly limited. For example, the decomposition inhibitingmaterials may be mixed with the crude alkyladamantyl ester prior toinitiation of the distillation or may be fed to a distiller directly orthrough a distillation column, distillation tube or reflux line afterthe initiation of the distillation. Further, as the decompositioninhibiting materials, a plurality of compounds can be used incombination.

In the production method of the present invention, a mode in which thedistillation is carried out in the presence of the decompositioninhibiting materials is not particularly limited, and simpledistillation or fractional distillation is used. In the case of thefractional distillation, as a fractionating column, a thin-filmfractionating column such as a vigoureux-type fractional column, aconcentric fractional column, a spinning band fractional column and apacked fractional column or a plate fractionating column such as abubble-cap fractionating column and a porous plate-type fractionatingcolumn is suitably used. Particularly, when vacuum distillation isperformed, a thin-film fractionating column which undergoes littlepressure loss is suitably used. Further, a known distillation mode suchas a Kugel roll or thin-film distillation can be used without anylimitations.

In addition, distillation conditions including temperature, pressure anda reflux ratio are not particularly limited and may be determined asappropriate according to composition of the crude alkyladamantyl ester,types and amounts of the decomposition inhibiting materials, purity ofthe target compound to be obtained at the end, and the like. When thealkyladamantyl ester is the compound represented by the above formula(2), conditions including a temperature of 80 to 150° C. and a pressureof 0.01 to 100 mmHg are preferably used.

As effects of the decomposition inhibiting materials, in addition to theabove decomposition inhibiting effect, an effect of facilitatinghandling of the compound to be purified by decreasing the viscosity ofthe compound to be purified or forming the compound to be purified intoa solution or suspension through addition of the decompositioninhibiting materials can also be expected, for example, even when thetarget compound is solid at room temperature. In a case where such aneffect is expected, a liquid decomposition inhibiting material having aboiling point which is close to that of the target compound is suitablyadded, as a second decomposition inhibiting material, to the compound tobe purified.

Further, in the present invention, the decomposition inhibitingmaterials also have an effect of improving storage stability of thealkyladamantyl ester. From the viewpoint of such an effect, as thedecomposition inhibiting materials, a compound having an oxirane ring asa heterocyclic ring and an aromatic amine are particularly preferredamong the aforementioned decomposition inhibiting materials.

In this case, the decomposition inhibiting materials are added in suchan amount that can inhibit decomposition of a stored alkyladamantylester. The amount should be determined in consideration of efficacy ofdecomposition inhibiting materials to be used, solubility of thedecomposition inhibiting materials against the alkyladamantyl ester anduse of the alkyladamantyl ester. The amount is preferably 0.0001 to 100parts by weight, more preferably 0.001 to 10 parts by weight, based on100 parts by weight of the alkyladamantyl ester.

When it is not desirable that the decomposition inhibiting materialsremain upon use of the target compound, decomposition inhibitingmaterials which can be easily separated from the target compound arepreferably used so as to be able to remove the decomposition inhibitingmaterials easily by carrying out appropriate treatment before use of thetarget compound. As a method of separating the decomposition inhibitingmaterials from the target compound, methods which are the same as thosementioned above can be used.

EXAMPLES

The present invention will be further described with reference toExamples and Comparative Examples hereinafter. However, the presentinvention shall not be limited by these Examples in any way.

Synthesis Example 1

30 g of 2-adamantanone was dissolved in tetrahydrofuran anhydride. Then,200 ml of solution of methyl magnesium bromide dissolved intetrahydrofuran in an amount of 1 mol/liter was added thereto at roomtemperature. After 3 hours, 5 g of pyridine was added, 26 g ofmethacrylic acid chloride was then added, and the resulting mixture wasstirred at 50° C. for 3 hours. After the obtained reaction mixture wasconcentrated, hexane and a 1N ammonium chloride solution were added tothe mixture, and the resulting mixture was shaken to separate an organicphase. Then, the organic phase was washed with a 5% sodium hydroxidesolution and then with water, and it was confirmed that the pH of anaqueous phase became 8. The washed organic phase was concentrated so asto obtain crude 2-methyl-2-adamantyl methacrylate containing 90% byweight of 2-methyl-2-adamantyl methacrylate.

Synthesis Example 2

70 g of 2-ethyl-2-adamantanol was dissolved in toluene, 1 g ofp-toluenesulfonic acid was added, and water was removed by distillationby use of a Dean and Stark dehydrator under heating so as to obtain2-ethylideneadamantane. To 50 g of the obtained 2-ethylideneadamantane,500 g of methacrylic acid and 0.1 ml of concentrated sulphuric acid wereadded, and the resulting mixture was heated at 80° C. for 5 hours. Afterhexane was added to the obtained reaction mixture, the mixture waswashed with water, a 5% sodium hydroxide solution, and water in turn,and it was confirmed that the pH of an aqueous phase became 8. After thewashed organic phase was concentrated, unreacted 2-ethylideneadamantanewas partially removed by sublimation so as to obtain crude2-ethyl-2-adamantyl methacrylate containing 80% by weight of2-ethyl-2-adamantyl methacrylate.

Example 1

To 100 parts by weight of the crude 2-methyl-2-adamantyl methacrylateobtained in Synthesis Example 1, 0.05 parts by weight of3-ethyl-3-hydroxymethyloxetane was added as a decomposition inhibitingmaterial, and the resulting mixture was distilled under a reducedpressure.

The reduced-pressure distillation was carried out at a temperature of120° C. and a degree of vacuum of 0.3 mmHg by use of a 5-cm vigoureuxfractionating column and a whole-condensation-type reflux fractionatingdevice while air was being introduced by means of a glass capillary. Afirst distillate was removed, and a main distillate started to becollected at a point where purity of the 2-methyl-2-adamantylmethacrylate exceeded 80%. From the collected main distillate,2-methyl-2-adamantyl methacrylate with a purity of 95.3 wt % could beobtained.

Example 2

To 100 parts by weight of the crude 2-methyl-2-adamantyl methacrylateobtained in Synthesis Example 1, 0.03 parts by weight ofdiglycidyl-bisphenol-A-based epoxy compound (mixture comprisingdiglycidyl bisphenol A (86 wt %) and a dimer of diglycidyl bisphenol A(14 wt %)) was added as a decomposition inhibiting material, and theresulting mixture was distilled under a reduced pressure.

The reduced-pressure distillation was carried out at a temperature of120° C. and a degree of vacuum of 0.3 mmHg by use of a 5-cm vigoureuxfractionating column and a whole-condensation-type reflux fractionatingdevice while pure oxygen was being introduced by means of a glasscapillary. A first distillate was removed, and a main distillate startedto be collected at a point where purity of the 2-methyl-2-adamantylmethacrylate exceeded 80%. From the collected main distillate,2-methyl-2-adamantyl methacrylate with a purity of 95.7 wt % could beobtained.

Example 3

Distillation was carried out in accordance with Example 1 except that 1part by weight of 2-hexadecylthiirane was used as a decompositioninhibiting material based on 100 parts by weight of the crude2-methyl-2-adamantyl methacrylate in place of 0.05 parts by weight of3-ethyl-3-hydroxymethyloxetane, in Example 1. A first distillate wasremoved, and a main distillate started to be collected at a point wherepurity of the 2-methyl-2-adamantyl methacrylate exceeded 80%. From thecollected main distillate, 2-methyl-2-adamantyl methacrylate with apurity of 93.4 wt % could be obtained.

Examples 4 to 10

As shown in Table 1, to 100 parts by weight of the crude2-methyl-2-adamantyl methacrylate (indicated as “crude methyl compound”in Table 1) obtained in Synthesis Example 1 or 100 parts by weight ofthe crude 2-ethyl-2-adamantyl methacrylate (indicated as “crude ethylcompound” in Table 1) obtained in Synthesis Example 2, decompositioninhibiting materials shown in Table 1 were added in predeterminedamounts, and distillations were carried out under a reduced pressure.

The reduced-pressure distillations were carried out at a temperature of90 to 140° C. and a degree of vacuum of 0.1 to 0.3 mmHg by use of a 5-cmvigoureux fractionating column and a whole-condensation-type refluxfractionating device while air was being introduced by means of a glasscapillary. Purities of thus obtained main distillates are shown inTable 1. As shown in Table 1, by use of the decomposition inhibitingmaterials of the present invention, high purity alkyladamantyl ester canbe obtained.

TABLE 1 Purity of Target Com- pound Crude Decomposition fromAlkyladamantyl Inhibiting Material Main Ester 100 Amount Distill- Ex.Parts By Added ate No. Weight Type (pbw) (wt %) 4 Crude Methyl N,N′-naphthyl-p- 10 95.1 Compound phenylenediamine 5 Crude MethylMg₆Al₂(OH)₁₆CO₃.4H₂O 1 97.6 Compound 6 Crude Methyl diglycidyl bisphenolF 0.1 96.3 Compound 7 Crude Methyl tetraglycidyl 0.001 95.8 Compounddiaminodiphenylmethane 8 Crude Ethyl 7-oxabicyclo[4.1.0] 0.01 97.2Compound hepta-3-ylmethyl-7- oxabicyclo[4.1.0] heptane-3-carboxylate 9Crude Ethyl dioctylphenothiazine 5 93.4 Compound 10 Crude Ethyl1,4-bis{[(3-ethyl-3- 0.03 96.6 Compound oxetanyl)methoxy]methyl} benzeneEx.: Example pbw: parts by weight Note 1) crude methyl compound: crude2-methyl-2-adamantyl methacrylate obtained in Synthesis Example 1 Note2) crude ethyl compound: crude 2-ethyl-2-adamantyl methacrylate obtainedin Synthesis Example 2

Comparative Example 1

The crude 2-methyl-2-adamantyl methacrylate obtained in SynthesisExample 1 was distilled under a reduced pressure as it was. A firstdistillate was removed, and a main distillate started to be collected ata point where purity of the 2-methyl-2-adamantyl methacrylate exceeded80%. From the collected main distillate, purity of the purified2-methyl-2-adamantyl methacrylate was merely 85.3 wt %.

Examples 11 to 20

As shown in Table 2, to 100 parts by weight of the 2-methyl-2-adamantylmethacrylate (indicated as “methyl compound A” in Table 2) purified inExample 1 or 100 parts by weight of the 2-methyl-2-adamantylmethacrylate (indicated as “methyl compound B” in Table 2) purified inComparative Example 1, decomposition inhibiting materials were added soas to examine storage stabilities at 40° C.

As shown in Table 2, storage stability of alkyladamantyl ester isimproved by use of the decomposition inhibiting materials in the presentinvention.

TABLE 2 Decomposition Dis- Inhibiting Material color- AlkyladamantylAmount ation Ester Added after Ex. 100 Parts (parts by 3 No. By WeightType weight) Months 11 Methyl diglycidyl 0.01 Not Compound A bisphenol AOccurred 12 Methyl diglycidyl 100 Not Compound A bisphenol A Occurred 13Methyl tetraglycidyl 0.0001 Not Compound A diaminodiphenyl- Occurredmethane 14 Methyl styrene oxide 0.1 Not Compound A Occurred 15 Methyl3-ethyl-3- 0.001 Not Compound A hydroxymethyl- Occurred oxetane 16Methyl Mg₆A₁₂(OH)₁₆ 0.01 Not Compound A CO₃.4H₂O Occurred 17 Methyltetramethyl- 5 Not Compound A hydroxide Occurred ammonium 18 MethylMg₆A₁₂(OH)₁₆ 0.02 Not Compound B CO₃.4H₂O Occurred 19 Methyl diglycidyl0.0001 Not Compound B bisphenol A Occurred 20 Methyl phenothiazine0.0001 Not Compound B Occurred C.Ex.2 Methyl Not Added — ColoredCompound A Brown C.Ex.3 Methyl Not Added — Colored Compound B Brown Ex.:Example C.Ex.: Comparative Example Note 1) methyl compound A: purified2-methyl-2-adamantyl methacrylate obtained in Example 1 Note 2) methylcompound B: purified 2-methyl-2-adamantyl methacrylate obtained inComparative Example 1

As described above, according to the present invention, a crudealkyladamantyl ester which contains impurities that decompose thealkyladamantyl ester and has been difficult to purify by distillationcan be easily purified by distillation. By use of the production methodof the present invention, a high purity alkyladamantyl ester which isexpected to be used as a resist material for a semiconductor can beobtained easily. Further, the alkyladamantyl ester can be stored stablyover a long time period.

What is claimed is:
 1. A method for producing a high purityalkyladamantyl ester which comprises the steps of esterifying acarboxylic acid or a derivative thereof with an adamantane compoundhaving an —OH group, —OM group or ═R group, wherein M is an alkali metalatom or MgX, wherein X represents a halogen atom, and R is a divalentaliphatic hydrocarbon group, and distilling a crude alkyladamantyl esterobtained to form a high purity alkyladamantyl ester, wherein thedistillation is carried out in the presence of a heterocyclic compoundwhich has, in a molecule, at least one saturated three-to-five-memberedheterocyclic ring having at least one hetero atom selected from thegroup consisting of oxygen, nitrogen, sulfur, selenium and silicon. 2.The method of claim 1, wherein the adamantane compound is2-alkyl-2-adamantanol, wherein the alkyl group has 1 to 6 carbon atoms,2-alkylideneadamantane, wherein the alkylidene group has 1 to 4 carbonatoms, or a compound represented by the following formula (1):

wherein R¹ is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and M is an alkali metal atom or MgX, wherein X represents ahalogen atom.
 3. The method of claim 1, wherein the crude alkyladamantylester is obtained by esterifying 2-alkyl-2-adamantanol, wherein thealkyl group has 1 to 6 carbon atoms, 2-alkylideneadamantane, wherein thealkylidene group has 1 to 4 carbon atoms, or a compound represented bythe following formula (1):

wherein R² is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and M is an alkali metal atom or MgX, wherein X represents ahalogen atom, with a carboxylic acid, a carboxylic acid halide, acarboxylic anhydride or a carboxylic acid ester.
 4. The method of claim1, wherein the alkyladamantyl ester is a compound represented by thefollowing formula (2):

wherein R² is a hydrogen atom or an alkyl group having 1 to 6 carbonatoms, and R³ is a hydrogen atom or a methyl group.
 5. The method ofclaim 1, wherein the heterocyclic ring is oxirane, oxetane, oxolane,thiirane, thiethane, thiolane, aziridine, azetidine or an N-alkylsubstituted compound thereof.
 6. The method of claim 1, wherein theheterocyclic compound does not react with the alkyladamantyl ester anddoes not decompose under distillation conditions.
 7. The method of claim1, wherein the heterocyclic compound exhibits such a high boiling pointthat does not allow the compounds to be distilled out at the time of thedistillation or has neither a boiling point nor a sublimation point. 8.The method of claim 1, which uses the heterocyclic compound in an amountof 0.0001 to 500 parts by weight based on 100 parts by weight of thecrude alkyladamantyl ester.
 9. An alkyladamantyl ester compositioncomprising 100 parts by weight of alkyladamantyl ester and 0.0001 to 100parts by weight of heterocyclic compound which has, in a molecule, atleast one saturated three-to-five-membered heterocyclic ring having atleast one hetero atom selected from the group consisting of oxygen,nitrogen, sulfur, selenium and silicon.